The present embodiments relate generally to data storage systems and more particularly, but not by way of limitation, to operating a head assembly, used in a data storage system, in a depopulated configuration.
Mass storage devices are one of many components of modern computers. One type of mass storage device is a disc drive. A typical disc drive includes a head stack assembly (HSA) that has one or more magnetic discs which are rotated by a spindle motor at a substantially constant high speed and accessed by an array of read/write heads which store data on tracks defined on the disc surfaces. A printed circuit board assembly (PCBA), which includes electronics used to control the operation of the HSA, is typically mounted to the underside of the HSA to complete the disc drive.
During early stages of a disc drive certification process, drives are tested for head performance and stability. If any one of the heads fails the test, the drive can be removed from the testing equipment to replace the HSA. The drive is then rebuilt with another HSA and tested again. This operation is very costly and in some cases it is more cost effective to leave the drive in the testing equipment, exclude the faulty head (depopulate), and continue with the certification process. Under this condition, if a default boot-up head (a head that is selected to carry out initial data access from one or more discs in the disc drive upon power up) is not faulty, information for the depopulated head is written on system tracks, on one or more discs of the HSA, in a depopulated head table where the default boot-up head has access. During any subsequent power up cycle, the default boot-up head reads information from the system track(s) where the depopulated head table is stored and thereby knows if any of the heads have been depopulated. Currently, in situations where the default boot-up head is faulty, information about the depopulated default boot-up head is stored in a serial flash (SF) memory on the PCBA to be retrieved during power up. This SF memory is only used during a power up cycle and therefore is an extra cost that the PCBA carries indefinitely for this purpose.
The present embodiments address these problems and offers other advantages over the prior art.